A Round Cushion

GemCad Ray Traces for RI = 1.76
Random Model Cosine Model ISO Model

A Round Cushion
Designed by Charles W. Covill covill@email.msn.com
Angles for R.I. = 1.76 49 facets + 16 facets on girdle = 65
4-fold, mirror-image symmetry 96 index
L/W = 1.000 T/W = 0.557 T/L = 0.557 P/W = 0.469 C/W = 0.140 H/W = (P+C)/W+0.02 = 0.629 P/H = 0.746 C/H = 0.222
Vol./W^3 = 0.230 Brightness at 0 degrees tilt for RI = 1.64
COS = 58.4 ISO = 70.6
Pavilion
1 45.00 02-22-26-46-50-70-74-94 Cut to meet at false culet.
2 43.83 06-18-30-42-54-66-78-90 Cut to meet with 1 at false culet.
g2 90.00 06-18-30-42-54-66-78-90 Complete level girdle line.
3 41.00 08-16-32-40-56-64-80-88 Meet 2 at girdle,make new culet.
Crown
g1 90.00 02-22-26-46-50-70-74-94 Determine size of stone.
1 32.21 96-24-48-72 Establish girdle thickness.
2 35.00 02-22-26-46-50-70-74-94 Meet 1 at girdle,continue level girdle
3 35.00 06-18-30-42-54-66-78-90 Meet 1 & 2,complete level girdle.
4 29.00 12-36-60-84 Meet 1,2 & 3. Also meet 3 at girdle.
t 0.00 Table  
With g1 cut 8 equal sides, Determine size of stone.
Cut pavilion facets 1 & 2 to meet at false culet.
Cut g2 to complete level girdle line.
Cut pavilion facet 3 to meet girdle and form new culet.


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Bob Keller